Origin of Modern Calculating
Machines

A chronicle of the evolution of the
principles that form the generic
make-up of the Modern
Calculating Machine

BY
J. A. V. TURCK
Member of The Western Society of Engineers

CHICAGO, 1921
Published under the auspices of
The Western Society of Engineers

Copyright, 1921, by
J. A. V. Turck

Stone Age Calculating

Foreword

There is nothing romantic in figures, and the average man takes little interest in any subject pertaining to them. As a result of this antipathy, there is plenty of historic evidence of man’s endeavor to minimize the hated drudgery of calculation.

While history shows that, from prehistoric man down to the present age, human ingenuity has turned to mechanical means to overcome the brain fatigue of arithmetical figuring, it is within quite recent years that he has really succeeded in devising means more rapid than the human brain.

Of this modern product little has been written, except in disconnected articles that have in no case offered a complete understanding as to who were the great benefactors of mankind that gave to the world the first concrete production of these modern principles of mechanical calculation.

The writer, believing that there are many who would be interested to know the true facts relative to this subject, has given to the public, in that which follows, a chronicle of the evolution of the principles disclosed in these modern machines, along with the proofs that form the foundation for the story in a way that all may understand.

Although the subject has been handled in a way that makes it unnecessary for the reader to be carried through a jangle of tiresome mechanical construction, the writer believes that there are many interested in the detail workings of these machines, and has for that reason provided an interesting and simple description of the working of each illustrated machine, which may be read by those who wish, or skipped over, if the reader desires, without the danger of losing knowledge of the relation of each of these machines to the Art.

Chapters

Illustrations

The Modern Accounting Machine

The term “adding machine” or “calculating machine” to most of us represents the machine we have seen in the bank. The average person is not familiar with the different types of accounting machines, to say nothing of the many uses to which they are put; but he has a vague idea that to hold any value they should produce a printed record, he doesn’t know why and he hasn’t stopped to reason why; but those he has seen in the bank do print, and any machine the bank uses, to his mind, must be all right.

There are, of course, people who do know the different types of accounting machines, and are familiar with their special uses, but there are very few who are familiar with the true history of the modern accounting machine.

General knowledge lacking

Articles written by those not familiar with the true facts relative to the art of accounting machines have wrought confusion. Their errors have been copied and new errors added, thus increasing the confusion. Again, claims made in trade advertisements and booklets are misleading, with the result that the truth is but little known.

These facts, and the psychological effect of seeing a certain type of machine in the bank would lead the average man to believe that the recording-adding machine was the only practical machine; and also (as someone stated in the December, 1915, issue of the Geographic Magazine) that Burroughs was the inventor of the recording-adding machine.

Although the history of accounting machines dates way back into the tenth century, the modern accounting machines are of quite recent origin, and are especially distinguished by the presence of depressable keys. The keys in these machines act as a means of gauging the actuation which determines the value in calculation, whether the machine is key-driven or key-set with a crank or motor drive.

These modern machines, which come within the classification of key-driven and key-set, have their respective special uses.

Key-driven machine first of the modern machines

The key-driven machine, which was the first produced of these two types of modern machines, does not print, and is used for all forms of calculation, but is generally behind the scenes in the accounting rooms of all lines of business, and for that reason is not so well known as the key-set crank-operated or motor-driven machine, which is designed to print and is always in full view in the bank where it is used to print your statement of account from the vouchers you have issued.

When we stop to analyze the qualities of these two types of machines, we find that each has its place and that neither may truly serve to displace the other. The organization of each is designed with reference to the special work it was intended to do.

The calculating machine, having only to perform the work of revolving the numeral wheels in calculating addition, subtraction, multiplication and division in its many forms and combinations, may be key-driven (on account of the slight mechanical resistance met with in action), and thus, as a one-motion machine, requiring only the depression of the keys, may also be much more rapid of manipulation than the two-motion recording-adding machine which, after depressing the keys for each item, requires the secondary operation of pulling a crank forward or operating a push bar that connects the motor.

The recording-adding machine being designed to print the items and answers of addition, requires power for the printing which cannot be supplied by key depression. Thus an extra means for supplying that power must be provided in the form of a crank lever, or in the latest machines by a motor. The keys in such machines serve only as digital control to gauge the setting of mechanism which prints the items and adds them together. The secondary motion operates the mechanism to print and add and finally to clear the machine for the setting up of the next item. The recording of added columns of figures requires that the answer must always be printed. This demands special operation of devices provided for that purpose, which also adds to the time spent in the operation of such machines as compared with the key-driven calculator.

Recording, the primary feature of adding machines that print

To state which of these two types of machines is the more useful would cause a shower of comment, and has nothing to do with the object of this article. Suffice it to say that where a printed record of items added together with their answer is required for filing purposes, or to bring together loose items like those in your bank statement, the recording-adding machine serves; but when rapid calculation in addition, multiplication, subtraction or division, or when combinations of these forms of calculation are required, the key-driven calculator is the practical machine for such work.

Although the key-driven calculator is generally not so well known, it is, as stated, the oldest of the modern accounting machines, and its usefulness places it in the accounting room, where it is oft-times found employed by the hundreds in figuring up the day’s work of accounting.

Validity and priority of invention

The purpose of this book is based wholly upon showing the validity and priority of invention which constitute true contributions to the Art of these two types of modern accounting machines; to place the facts for once and all time before the public in such a way that they may judge for themselves to whom the honor is due and thus settle the controversy that exists.

The quibbling of court contests over the terminology of claims of patents owned by the various inventors have been set aside and only the true contributions to the Art which pertain to the fundamental principles that have made the modern machines possible, are here dealt with.

The dates of patents on inoperative or impractical machines have from time to time been held up to the public as instances of priority of invention; but when the validity of these patents, as furnishing any real contributions to the Art, is questioned, they are not found to hold the theme or principle that made the modern machines possible, and as inventions, fade into obscurity.

Figure 1

Figure 2

One of the Pascal Machines

The Art of either the calculating machine or the adding-recording machine is not new; it is, as a matter of fact, very old. As before stated, the Art of “accounting machine” dates back to the tenth century, but the first authentic evidence of a working machine is extant in models made by Pascal in 1642 ([see illustration]).

The Pascal Machine

Referring to the illustration, [Fig. 1], of Pascal’s machine on the opposite page, it will be noted that there are a series of square openings in the top of the casing; under these openings are drums, each numbered on its cylindrical surface.

Description of Pascal’s invention

As the machine illustrated was made to figure English currency, the two right-hand wheels are numbered for pence and shillings, while the six wheels to the left are numbered from 1 to 9 and 0 for pounds.

Blaise Pascal

The pounds register-drums, or numeral wheels, are each operated by a train of gearing connecting them with a ten-armed turnstile wheel which form the hub and spokes of what appears to be a series of wheels on the top of the casing. While the spokes and hub are movable, the rims of these wheels are stationary and are numbered from 1 to 9 and 0.

The geared relation between the turnstile wheels and the numeral wheels is such that rotating a turnstile will give like rotation to its numeral wheel.

Assuming that the numeral wheel of any one of the different orders registered 0 through its sight opening and the turnstile of the same order was moved one spoke of a rotation, it would move the wheel so that the 0 would disappear and the figure 1 would appear; now if we should move the same turnstile three more spokes the numeral wheel would move likewise three spaces and the 4 would appear.

A stop in the form of a finger reaching over the spokes is provided to stop the turnstile at the right point so that the figures on the numeral wheels may register properly with the sight openings in the casing.

Constructional features of the Pascal machine

The figures on the wheel rims fast to the casing are arranged anti-clockwise to register with the space between the spokes, the 0 registering with the first space, the 1 with the second space and so on around the wheel. Thus by use of the finger or a stylo inserted in a space opposite the number to be added, the operator may move the spoked wheel or turnstile clockwise until stopped by the stop finger. By repeated selection and operation for each figure to be added, the wheels will be revolved through their cycles of rotation caused by the accumulation.

As the numeral wheels complete each rotation the 0 will appear, so that a registration of the tens must be made. Pascal provided for the accumulation of the tens by automatically turning the wheel of next higher order one point through the action of the lower wheel.

The novel means employed for this transfer of the tens consisted of a one-step ratchet device operated by a pin in the train of gearing connected with the lower numeral wheel, which, as the lower wheel passed from 9 to 0, forced the lever to which the ratchet pawl was attached in a direction to cause the gearing of the higher numeral wheel to be ratcheted forward far enough to add one to the higher numeral wheel.

The direct actuation of a numbered wheel through its various degrees of rotation and the secondary feature of effecting a one-step movement to the numbered wheel of higher order (which seems to have been originated by Pascal) is the foundation on which nearly all the calculating machines have since been constructed to calculate the combinations of the Arabian numerals represented in Addition, Multiplication, Subtraction and Division.

In [Fig. 2] of the illustration of Pascal’s machine, the machine has been reversed, and the bottom of the casing, which is hinged, thrown back, showing the numeral wheels and gearing of the different orders and the transfer levers for the carry of the tens.

Increased capacity of modern calculator

The Art of the modern machines is far removed from the older Art by its greatly increased capacity for rapid calculation which is found emanating from the provision of keys as the means of manipulation.

To the unsophisticated, such a simple thing as applying keys to the ancient type of calculating machines that have been made and used for centuries, would seem but a simple mechanical application that the ordinary mechanic could accomplish. But it was too great a problem for the many renowned inventors of the older Art to solve.

Even though the use of depressable keys was common to many machines, especially the piano, they knew that the organized make-up of their machines could scarcely stand, without error, the slow action received from the crank motion or other means employed as manipulating devices. To place it within the power of an operator to operate their machines at such a speed as would obtain in the sudden striking of a key would result in chaos.

Patent office a repository of ineffectual efforts

There is no room for doubt that some of these early inventors had the wish or desire to produce such a key-driven machine and may have attempted to produce one. But as they lacked the advantage of an institution like the Patent Office in which they could leave a record of their inoperative inventions, and in view of the fact that they were dependent on producing an operating machine for credit, there is no authentic proof that they made attempts in this line.

Parmelee Patent Drawings

The Early Key-Driven Art

M. Le Colonel D’Ocagne, Ingénieur des Ponts et Chaussées, Professeur à l’École des Ponts et Chaussées, Répétiteur à l’École Polytechnique, in his “Le Calcul simplifie,” a historical review of calculating devices and machines, refers to the key-driven machine as having first made its appearance in the Schilt machine of 1851, but that the Art reached its truly practical form in America. In the latter part of his statement the professor is correct, but as to the first appearance of the key-driven machine the U. S. Patent Office records show that a patent was issued to D. D. Parmelee in 1850 for a key-driven adding machine ([see illustration]).

The Parmelee Machine

First attempt to use depressable keys for adding was made in America

By referring to the illustration of the [Parmelee machine] reproduced from the drawings of the patent, the reader will notice that the patentee deviated from the established principle of using numeral wheels. In place of numeral wheels a long ratchet-toothed bar has been supplied, the flat faces of which are numbered progressively from the top to the bottom.

Description of Parmelee machine

As shown in [Fig. 2] of these drawings, a spring-pressed ratchet pawl marked k, engages the teeth of the ratchet or numeral bar. The pawl k, is pivoted to a lever-constructed device marked E, the plan of which is shown in [Fig. 3]. This lever device is pivoted and operated by the keys which are provided with arms d, so arranged that when any one of the keys is depressed the arm contacts with and operates the lever device and its pawl k to ratchet the numeral bar upwards.

Another spring-pressed ratchet pawl marked m ([see Fig. 2]) is mounted on the bottom of the casing and serves to hold the numeral bar from returning after a key-depression.

It will be noted from [Fig. 1] that the keys extend through the top of the casing in progressively varying heights. This variation is such as to allow the No. 1 key to ratchet up one tooth of the numeral bar, the No. 2 key two teeth, etc., progressively. By this method a limited column of digits could be added up by depressing the keys corresponding to the digits and the answer could be read from the lowest tooth of the numeral bar that protruded through the top of the casing.

It is evident that if the Parmelee machine was ever used to add with, the operator would have to use a pussyfoot key-stroke or the numeral bar would over-shoot and give an erroneous answer, as no provision was made to overcome the momentum that could be given the numeral bar in an adding action.

Foreign digit adders
Single digit adders lack capacity

The foreign machines of the key-driven type were made by V. Schilt, 1851; F. Arzberger, 1866; Stetner, 1882; Bagge, 1882; d’Azevedo, 1884; Petetin, 1885; Maq Meyer, 1886. These foreign machines, like that of Parmelee, according to M. le Colonel d’Ocagne, were limited to the capacity of adding a single column of digits at a time. That is, either a column of units or tens or hundreds, etc., at a time. Such machines, of course, required the adding first of all the units, and a note made of the total; then the machine must be cleared and the tens figure of the total, and hundreds, if there be one, must then be added or carried over to the tens column the same as adding single columns mentally.

On account of these machines having only a capacity for adding one order or column of digits, the unit value 9 was the greatest item that could be added at a time. Thus, if the overflow in adding the units column or any other column amounted to more than one place, it required a multiple of key-depressions to put it on the register. For example, suppose the sum of adding the units columns should be 982, it would require the depression of the 9-key ten times and then the 8-key to be struck, to put the 98 on the machine. This order of manipulation had to be repeated for each denominational column of figures.

Another method that could be used in the manipulation of these single-order or digit-adding machines was to set down the sum of each order as added with its units figure arranged relative to the order it represents the sum of, and then mentally add such sums (see example below) the same as you would set down the sums in multiplication and add them together.

Example of method that may be used with single column adder.

• 982
• 563
• 384
• 125
• ———
• 170012

Such machines, of course, never became popular because of their limited capacity, which required many extra movements and caused mental strain without offering an increase in speed of calculation as compared with expert mental calculation. There were a number of patents issued in the United States on machines of this class which may well be named single digit adders.

Some early U.S. patents on single-digit adding machines

The machines of this type which were patented in the United States, preceding the first practical multiple order modern machine, were patented by D. D. Parmelee, 1850; W. Robjohn, 1872; D. Carroll, 1876; Borland & Hoffman, 1878; M. Bouchet, 1883; A. Stetner, 1883; Spalding, 1884; L. M. Swem, 1885 and 1886; P. T. Lindholm, 1886; and B. F. Smith, 1887. All of these machines varied in construction but not in principle. Some were really operative and others inoperative, but all lacked what may be termed useful capacity.

To those not familiar with the technical features of the key-driven calculating machine Art, it would seem that if a machine could be made to add one column of digits, it would require no great invention or ingenuity to arrange such mechanisms in a plurality of orders. But the impossibility of effecting such a combination without exercising a high degree of invention will become evident as the reader becomes familiar with the requirements, which are best illustrated through the errors made by those who tried to produce such a machine.

As stated, the first authentic knowledge we have of an actual machine for adding is extant in models made by Pascal in 1642, which were all multiple-order machines, and the same in general as that shown in the [illustration, page 10].

Calculating machines in use abroad for centuries

History shows that Europe and other foreign countries have been using calculating machines for centuries. Like that of Pascal’s, they were all multiple-order machines, and, although not key-driven, they were capable of adding a number of columns or items of six to eight places at once without the extra manipulation described as necessary with single-order digit adding machines. A number of such machines were made in the United States prior to the first practical multiple-order key-driven calculator.

First key-driven machines no improvement to the Art

This fact and the fact that the only operative key-driven machines made prior to 1887 were single-digit adders are significant proof that the backward step from such multiple-order machines to a single-order key-driven machine was from the lack of some unknown mechanical functions that would make a multiple-order key-driven calculator possible. There was a reason, and a good one, that kept the inventors of these single-order key-driven machines from turning their invention into a multiple-order key-driven machine.

It is folly to think that all these inventors never had the thought or wish to produce such a machine. It is more reasonable to believe there was not one of them who did not have the wish and who did not give deep thought to the subject. There is every reason to believe that some of them tried it, but there is no doubt that if they did it was a failure, or there would be evidence of it in some form.

The Hill Machine

The U. S. Patent Office records show that one ambitious inventor, Thomas Hill, in 1857 secured a patent on a multiple-order key-driven calculating machine ([see illustration]), which he claimed as a new and useful invention. The Hill patent, however, was the only one of that class issued, until the first really operative modern machine was made thirty years later, and affords a fine example by which the features that were lacking in the make-up of a really operative machine of this type may be brought out.

Description of the Hill machine

The [illustrations of the Hill machine] on the opposite page, reproduced from the drawings of the patent, show two numeral wheels, each having seven sets each of large and small figures running from 1 to 9 and the cipher marked on their periphery. The large sets of figures are arranged for addition or positive calculation, and the small figures are arranged the reverse for subtraction or negative calculation. The wheels are provided with means for the carry of the tens, very similar to that found in the Pascal machine. Each of the two wheels shown are provided with ratchet teeth which correspond in number with the number of figures on the wheel.

Spring-pressed, hook-shaped ratchet pawls marked b, are arranged to be in constant engagement with the numeral wheels. These pawls are each pivotally mounted in the end of the levers marked E, which are pivoted at the front end of the casing.

Hill Patent Drawings

The levers E, are held in normal or upward position by springs f, at the front of the machine. Above each of these levers E, are a series of keys which protrude through the casing with their lower ends resting on the levers. There are but six keys shown in the drawing, but the specification claims that a complete set of nine keys may be supplied for each lever.

The arrangement and spacing of the keys are such that the greater the value of the key the nearer it is to the fulcrum or pivot of the lever E. The length of the key stem under the head or button of each key is gauged to allow depression of the key, the lever E and pawl b, far enough to cause the numeral wheel to rotate as many numeral places as the value marking on the key.

A back-stop pawl for the numeral wheels, marked p, is mounted on a cross-rod at the top of the machine. But one of these pawls are shown, the shaft and the pawl for the higher wheel being broken away to show the device for transferring the tens to the higher wheel.

The transfer device for the carry of the tens is a lever arrangement constructed from a tube F, mounted on the cross-rod m, with arms G and H. Pivoted to the arm G, is a ratchet pawl i, and attached to the pawl is a spring that serves to hold the pawl in engagement with the ratchet of the higher-order numeral wheel, and at the same time, through its attachment with the pawl, holds the lever arms G and H retracted as shown in the drawing.

As the lower-order numeral wheel passes any one of its points from 9 to O, one of the teeth or cam lugs n, on the wheel will move the arm H, of the transfer lever forward, causing the pawl i, to move the higher-order wheel one step to register the accumulation of the tens.

The functions of the Hill mechanism would, perhaps, be practical if it were not for the physical law that “bodies set in motion tend to remain in motion.”

Hill machine at National Museum

Considerable unearned publicity has been given the Hill invention on account of the patent office model having been placed on exhibit in the National Museum at Washington. Judging from the outward appearance of this model, the arrangement of the keys in columns would seem to impart the impression that here was the foundation of the modern key-driven machine. The columnar principle used in the arrangement of the keys, however, is the only similarity.

Inoperativeness of Hill machine

The Hill invention, moreover, was lacking in the essential feature necessary to the make-up of such a machine, a lack that for thirty years held the ancient Art against the inroads of the modern Art that finally displaced it. The feature lacking was a means for controlling the action of the mechanism under the tremendously increased speed produced by the use of depressable keys as an actuating means.

Hill made no provision for overcoming the lightning-speed momentum that could be given the numeral wheels in his machine through manipulation of the keys, either from direct key-action or indirectly through the carry of the tens. Imagine the sudden whirl his numeral wheel would receive on a quick depression of a key and then consider that he provided no means for stopping these wheels; it is obvious that a correct result could not be obtained by the use of such mechanism. Some idea of what would take place in the Hill machine under manipulation by an operator may be conceived from the speed attained in the operation of the keys of the up-to-date modern key-driven machine.

High speed of key drive

Operators on key-driven machines oftentimes attain a speed of 550 key strokes a minute in multiplication. Let us presume that any one of these strokes may be a depression of a nine key. The depression and return, of course, represents a full stroke, but only half of the stroke would represent the time in which the wheel acts. Thus the numeral wheel would be turned nine of its ten points of rotation in an eleven hundredth (¹/₁₁₀₀) of a minute. That means only one-ninth of the time given to half of the key-stroke, or a ninety-nine hundredth (¹/₉₉₀₀) of a minute; a one hundred and sixty-fifth (¹/₁₆₅) part of a second for a carry to be effected.

Camera slow compared with carry of the tens

If you have ever watched a camera-shutter work on a twenty-fifth of a second exposure, which is the average time for a snap-shot with an ordinary camera, it will be interesting to know that these controlling devices of a key-driven machine must act in one-fifth the time in which the shutter allows the daylight to pass through the lens of the camera.

Think of it; a machine built with the idea of offering the possibility of such key manipulation and supplying nothing to overcome the tremendous momentum set up in the numeral wheels and their driving mechanism, unless perchance Hill thought the operator of his machine could, mentally, control the wheels against over-rotation.

Chapin Patent Drawings

Lack of a proper descriptive term used to refer to an object, machine, etc., oftentimes leads to the use of an erroneous term. To call the Hill invention an adding machine is erroneous since it would not add correctly. It is as great an error as it would be to refer to the Langley aeroplane as a flying machine.

Hill machine merely adding mechanism, incomplete as operative machine

When the Wright brothers added the element that was lacking in the Langley plane, a real flying machine was produced. But without that element the Langley plane was not a flying machine. Likewise, without means for controlling the numeral wheels, the Hill invention was not an adding machine. The only term that may be correctly applied to the Hill invention is “adding mechanism,” which is broad enough to cover its incompleteness. And yet many thousands of people who have seen the Hill invention at the National Museum have probably carried away the idea that the Hill invention was a perfectly good key-driven adding machine.

Chapin and Stark patents

Lest we leave unmentioned two machines that might be misconstrued to hold some of the features of the Art, attention is called to patents issued to G. W. Chapin in 1870 ([see illustration on opposite page]), and A. Stark in 1884 ([see illustration on page 32]).

Chapin Machine

Description of Chapin machine

Referring to the illustration reproducing the drawings of the Chapin patent, the reader will note that in [Fig. 1] there are four wheels marked V. These wheels, although showing no numerals, are, according to the specification, the numeral wheels of the machine.

The wheels are provided with a one-step ratchet device for transferring the tens, consisting of the spring frame and pawl shown in [Fig. 3], which is operated by a pin in the lower wheel.

In [Fig. 1] the units and tens wheel are shown meshed with their driving gears. These gears are not numbered but are said to be fast to the shafts N and M, respectively ([see Fig. 2]).

Fast on the shaft M, is a series of nine ratchet-toothed gears marked O, and a like series of gears P, are fast to the shaft N. Co-acting with each of these ratchet-toothed gears is a ratchet-toothed rack F, pivoted at its lower end to a key-lever H, and pressed forward into engagement with its ratchet gear by a spring G.

The key-levers H, of which there are two sets, one set with the finger-pieces K and the other with the finger-pieces J, are all pivoted on the block I, and held depressed at the rear by an elastic band L. The two sets of racks F, are each provided with a number of teeth arranged progressively from one to nine, the rack connected with the No. 1 key having one ratchet tooth, the No. 2 having two teeth, etc.

Inoperativeness of Chapin machine

By this arrangement Chapin expected to add the units and tens of a column of numerical items, and then by shifting the numeral wheels and their transfer devices, which are mounted on a frame, designed for that purpose, he expected to add up the hundred and thousands of the same column of items.

It is hardly conceivable that the inventor should have overlooked the necessity of gauging the throw of the racks F, but such is the fact, as no provision is made in the drawings, neither was mention made of such means in the specification. Even a single tooth on his rack F, could, under a quick key-stroke, overthrow the numeral wheels, and the same is true of the carry transfer mechanism.

From the Stark Patent Drawings

The Chapin machine, like that of Hill, was made without thought as to what would happen when a key was depressed with a quick stroke, as there was no provision for control of the numeral wheels against overthrow. As stated, the machine was designed to add two columns of digits at a time, and with an attempt to provide means to shift the accumulator mechanism, or the numeral wheels and carry-transfer devices, so that columns of items having four places could be added by such a shift. Such a machine, of course, offered less than could be found in the Hill machine, and that was nothing at all so far as a possible operative machine is concerned.

The Stark Machine

The [reproduction of the patent drawings] of the Stark machine illustrated on the opposite page show a series of numeral wheels, each provided with three sets of figures running from 1 to 9 and 0.

Description of Stark machine

Pivotally mounted upon the axis of the numeral wheels at each end are sector gears E¹ and arms E⁴, in which are pivoted a square shaft E, extended from one arm to the other across the face of the numeral wheels. The shaft E, is claimed to be held in its normal position by a spring so that a pawl, E², shiftably mounted on the shaft, designed to ratchet or actuate the numeral wheels forward, may engage with any one of the numeral wheel ratchets.

A bail marked D, is pivoted to standards A¹, of the frame of the machine, and is provided with the two radial racks D³ which mesh with the sector gears E¹. It may be conceived that the act of depressing the bail D, will cause the actuating pawl E², to operate whichever numeral wheel it engages the ratchet of.

The bail D, is held in its normal position by a spring D², and is provided with nine keys or finger-pieces d, eight of which co-act with the stepped plate G, to regulate the additive degree of rotation given to the numeral wheels, while the ninth has a fixed relation with the bail and the bail itself is stopped.

The keys d, marked from 1 to 8, are pivoted to the bail in such a manner that their normal relation to the bail will allow them to pass by the steps on the stepped plate G, when the bail is depressed by the fixed No. 9 key. When, however, any one of the keys numbered from 1 to 8 is depressed, the lower end of the shank of the key will tilt rearward, and, as the bail is depressed, offers a stop against the respective step of the plate G, arranged in its path, thus stopping further action of the actuating pawl E², but offering nothing to prevent the continuation of the force of momentum set up in the numeral wheels by the key action.

There was small use in stopping the action of the pawl E², if the ratchet and numeral wheel, impelled by the pawl, could continue onward under its momentum.

The carry of the tens transfer device is of the same order as that described in the Pascal and Hill machines; that is, a one-step ratchet-motion actuated by a cam lug or pin from the lower wheel. The carry transfer device consists of the lever F, and pawl f⁴, acting on the ratchet of the upper wheel which is operated by the cam lugs b⁵ of the lower wheel acting on the arms f¹ and f³ of the lever F.

From the Robjohn Patent Drawings

Inoperativeness of Stark machine

The machine shown in the Stark patent was provided with but one set of keys, but the arrangement for shifting the driving ratchet pawl E², from one order to another, so that the action of the keys may rotate any one of the numeral wheels, gave the machine greater capacity than the single digit adders; but as with the Chapin machine, of what use was the increase in capacity if the machine would not add correctly. That is about all that may be said of the Stark machine, for since there was no means provided by which the rotation of numeral wheels could be controlled, it was merely a device for rotating numeral wheels and was therefore lacking in the features that would give it a right to the title of an adding machine.

Nine keys common to a plurality of orders

The nine-key scheme of the Stark invention, connectable to the different orders, was old, and was first disclosed in the U. S. Patent to O. L. Castle in 1857 (a machine operated by a clock-spring wound by hand), but its use in either of these machines should not be construed as holding anything in common with that found in some of the modern recording adders. The Castle machine has not been illustrated because it does not enter into the evolution of the modern machine.

The ancient Art, or the Art prior to the invention of Parmelee, consisted of mechanism which could be controlled by friction devices, or Geneva gear-lock devices, that were suitable to the slow-acting type of manipulative means.

The first attempt at a positive control for a key-driven adding device is found in a patent issued to W. Robjohn in 1872 ([see illustration]). As will be noted, this machine was referred to in the foregoing discussion as merely a single-digit adding machine, having the capacity for adding but one column of digits at a time.

Robjohn Machine

Referring to the [illustration of the patent drawings] of the Robjohn machine, it will be noted that there are three sight openings in the casing through which the registration of the numeral wheels may be read. The numeral wheels, like those of all machines of this character, are connected by devices of a similar nature to those in the Hill machine for carrying the tens, one operating between the units and tens wheel and another between the tens and hundredths wheel.

Description of Robjohn machine

The units wheel shown in [Fig. 3] is connected by gearing to a long pin-wheel rotor, marked E, so that any rotation of the rotor E, will give a like rotation to the units numeral wheel to which it is entrained by gearing.

To each of the nine digital keys, marked B, is attached an engaging and disengaging sector gear device, which, as shown in [Fig. 3], although normally not in engagement with the rotor E, will upon depression of its attached key, engage the rotor and turn it.

A stop device is supplied for the key action, which in turn was supposed to stop the gear action; that seems rather doubtful. However, an alternative device is shown in [Figs. 4 and 5], which provides what may without question be called a stop device to prevent over-rotation of the units wheel under direct key action.

From Drawings of Bouchet Patent 314,561

It will be noted that the engaging and disengaging gear device is here shown in the form of a gear-toothed rack and that the key stem is provided with a projecting arm ending in a downwardly projecting tooth or detent which may engage the rotor E, and stop it at the end of the downward key action. While the stopping of the rotor shows a control in the Robjohn machine which takes place under direct action from the keys to prevent overthrow of the units numeral wheel, it did not prevent the overflow of the higher or tens wheels, if a carry should take place. There was no provision for a control of the numeral wheels under the action received from the carry of the tens by the transfer mechanism.

First control for a carried numeral wheel

The first attempt to control the carried wheel in a key-driven machine is found in a patent issued to Bouchet in 1882 ([see illustration on opposite page]); but it was a Geneva motion gearing which, as is generally known, may act to transmit power and then act to lock the wheel to which the power has been transmitted until it is again to be turned through the same source. Such a geared up and locked relation between the numeral wheels, of course, made the turning of the higher wheel (which had been so locked) by another set of key-mechanism an impossibility.

Bouchet Machine

The [illustration of the Bouchet machine] on the opposite page was reproduced from the drawings of the patent which is the nearest to the machine that was placed on the market. The numeral wheels, like most of the single-digit adders, are three in number, and consist of the prime actuated, or units wheel, and two overflow wheels to receive the carry of the tens. The units wheel has fixed to it a long 10-tooth pinion or rotor I, with which nine internal segmental gear racks L, are arranged to engage and turn the units wheel through their nine varying additive degrees of rotation.

Description of Bouchet machine

The segmental gear racks L, are normally out of mesh with the pinion I, and are fast to the key levers E, in such a manner that the first depression of a key causes its rack to rock forward and engage with the pinion I, and further depression moves the rack upward and rotates the pinion and units numeral wheel. It will be noted that this engaging and disengaging gear action is in principle like that of Robjohn.

The transfer devices for the carry of the tens, as already stated, belong to that class of mechanism commonly known as the “Geneva motion.” It consists of a mutilated or one-tooth gear fast to the units wheel operating with a nine-tooth gear, marked D¹, loosely mounted on an axis parallel to the numeral wheel axis. Each revolution of the units wheel moves the nine-tooth gear three spaces, and in turn moves the next higher numeral wheel to which it is geared far enough to register one point or the carry. A circular notched disc, marked S, is fast to the units wheel, and the nine-tooth gear D¹, has part of two out of every three of its teeth mutilated or cut away to make a convex surface for the notched disc to rotate in.

With such construction the nine-tooth gear may not rotate or become displaced as long as the periphery of the disc continues to occupy any one of the three convex spaces of the nine-tooth gear. When, however, the notch of the disc is presented to the mutilated portion of the nine-tooth gear, the said gear is unlocked. This unlocking is coincident to the engagement of the single tooth of the numeral wheel-gear with the nine-tooth gear and the passing of the numeral wheel from 9 to 0, during which the nine-tooth gear will be moved three spaces, and will be again locked as the notch in the disc passes and the periphery fills the next convex space of the mutilated nine-tooth gear.

Bouchet machine marketed

The Bouchet machine was manufactured and sold to some extent, but never became popular, as it lacked capacity. Machines of such limited capacity could not compete with ordinary accountants, much less with those who could mentally add from two to four columns at a clip. Aside from the capacity feature, there was another reason why these single-order machines were useless, except to those who could not add mentally. Multiple forms of calculation, that is, multiplication and division, call for a machine having a multiplicity of orders. The capacity of a single order would be but 9 × 9, which requires no machine at all—a seven-year-old child knows that. To multiply 58964 × 6824, however, is a different thing, and requires a multiple-order calculator.

Misuse of the term “Calculating Machine”

It is perhaps well at this time to point out the misuse of the term calculating where it is applied to machines having only a capacity for certain forms of calculating as compared with machines which perform in a practical way all forms of calculation, that is, addition, multiplication, subtraction and division. To apply the term “calculating machine” to a machine having anything less than a capacity for all these forms is erroneous.

An adding machine may perform one of the forms of calculation, but to call it a calculating machine when it has no capacity for division, subtraction or multiplication, is an error; and yet we find the U. S. Patent Office records stuffed full of patents granted on machines thus erroneously named. The term calculating is the broad term covering all forms of calculation, and machines performing less should be designated according to their specific capacities.

It is true that adding is calculating, and under these circumstances, why then may not an adding machine be called a calculator? The answer is that it may be calculating to add; it may be calculating to either subtract, multiply or divide; but if a machine adds and is lacking in the means of performing the other forms of calculation, it is only part of a calculating machine and lacks the features that will give it title to being a full-fledged calculator.[1]

Considerable contention was raised by parties in a late patent suit as to what constituted the make-up of a calculating machine. One of the attorneys contended that construction was the only thing that would distinguish a calculating machine. But as machines are named by their functioning, the contention does not hold water. That is to say: A machine may be a calculating machine and yet its construction be such that it performs its functions of negative and positive calculation without reversal of its action.

Again, a machine may be a calculating machine and operate in one direction for positive calculation and the reverse for negative calculation. As long as the machine has been so arranged that all forms of calculation may be performed by it without mental computation, and the machine has a reasonable capacity of at least eight orders, it should be entitled to be called a calculating machine.

Drawings of Spalding Patent No. 293,809

The Spalding Machine

The next machine that has any bearing on the key-driven Art of which there is a record, is illustrated in a patent granted to C. G. Spalding in 1884 ([see illustration on opposite page]). The Spalding invention, like that of Bouchet, was provided with control for its primary actuation and control for its secondary or carrying actuation.

Description of Spalding machine

Referring to the [Spalding machine] reproduced from the drawings of his patent, the reader will note that in place of the units and tens numeral wheels, a clock hand has been supplied, co-operating with a dial graduated from 0 to 99, showing the figures 5, 10, 15, etc., to 95, for every five graduations.

Another similar hand or arrow and dial to register the hundreds is also provided, having a capacity to register nineteen hundred. Attached to the arrows, through a shaft connection at the back of the casing are ratchet wheels, having respectively the same number of teeth as the graduation of the dial to which each hand belongs.

Co-operating with the hundred-tooth ratchet of the units and tens register hand is a ratchet and lever motion device ([see Fig. 2]) to turn the arrow from one to nine points of the graduation of the dial. The ratchet and lever motion device consists of the spring-pressed pawl E, mounted on the lever arm D, engaging the hundred-tooth ratchet, the link or push-rod F, the lever G, and its spring O. It will be noted that a downward action of the lever G, will, through the rod F, cause a like downward action of the lever D, causing the ratchet pawl E to be drawn over the ratchet teeth. Upon the release of the lever G, the spring O, will return it to its normal position and through the named connecting parts, ratchet forward the arrow.

The normal position of the pawl E is jammed into the tooth of the ratchet and against the bracket C, that forms the pivot support for the pivot shaft of the arrow. This jammed or locked combination serves to stop the momentum of the ratchet wheel at the end of the ratcheting action, and holds the wheel and its arrow normally locked until the lever G is again depressed.

The means for gauging the depression and additive degrees of action of the lever G is produced through the slides or keys marked a, having finger-pieces c, springs f, and pins e, bearing against the top of the lever G, combined with what may be called a compensating lever marked K.

The specification of the patent states that the depression of a key will depress the lever G and the free end will engage the bent end t, of the compensating lever K, and rock its envolute curved arm M, upward until it engages the pin e of the key, which will block further motion of the parts.

The effectiveness of the construction shown for the lever K is open to question.

Prime actuation of a carried wheel impossible in the Spalding machine

The carry of the hundreds is accomplished by means of a one-step ratchet device represented by the parts lever R, pawl T, spring P, and operating pin g. When the hundred-tooth ratchet nears the end of its revolution, the pin g, made fast therein, engages the free end of the ratchet lever R, and depresses it; and as the hand attached to the hundred-tooth ratchet wheel passes from 99 to 0 the pin g passes off the end of the ratchet lever R, and the spring P retracts the lever ratcheting the twenty-tooth wheel and its arrow forward one point so that the arrow registers one point greater on the hundreds dial.

Although the Spalding means of control under carrying differed from that of Bouchet in construction, its function was virtually the same in that it locked the carried or higher wheel in such a manner as to prevent the wheel from being operated by an ordinal set of key mechanism.

And the control under key action would prevent a carry being delivered to that order through the locked relation of the ratchet and pawl E.

The Key-Driven Calculator

While these single-digit adding machines have been used to illustrate how the control, which was lacking in the Hill invention, had been recognized by other inventors as a necessary requisite to the key-drive, it should not be construed that such carrying control as had been applied to their inventions was of a type that could be used in the Hill machine or in any multiple-order key-driven machine. It was thirty years after the first attempt to control a key-driven machine was made before an operative multiple-order key-driven machine, with a control that would prevent over-rotation, was finally invented.

Theory versus the concrete

Theoretically, it would seem that the only feature or element lacking in the Art prior to 1886, to produce a real key-driven calculator was means that would control the carrying and also leave the carried wheel free for key actuation. It was, however, quite a different problem. Theoretical functions may be patched together to make a theoretical machine; but that is only theory and not the concrete.

All but one of the generic elements solved

To take fragmental parts of such machines as were disclosed in the Art and patch them together into anything practical was impossible, even if one had been familiar with the Art and could devise mechanism to supply the new element. That is, leaving aside the broad or generic theoretical elements, which today, from knowledge gained by later inventions, serve the make-up of a key-driven calculator, there was still lacking any concrete example or specific design of a whole machine, as there was no such machine disclosed in the drawings of patents, or any known mechanism which, if arranged in multiples, would be operative as a practical machine even if mechanism to supply the new element were to be added.

In other words, while it is conceded from our present knowledge that all but one of the generic theoretical elements had been solved as disclosed in the various before-named machines, it required the application of these elements in a different way from anything before disclosed; which in itself required a different concrete form of the generic principles for the whole machine as well as a generic form of invention covering the new theoretical element.

It may be easy to analyze that which exists, but quite a different story to conceive that which did not exist. With reference to the Art, however, the production of the new element is a feature that may be credited without question. The concrete does not enter into it other than as proof that a new feature has been created.

Originality of inventions

While the discussion of the Art from a scientific standpoint brings together in after years what has been accomplished by different inventors, it is doubtful whether any of these early inventors had other knowledge than what may possibly have been obtained from seeing one of the foreign-made crank-driven machines. All inventors work with an idea obtained from some source, but on the whole few copy inventions of others. When an Art is fully established, however, and machines representing the Art are to be found on the market and the principal features of such machines are portrayed in a later patent, it may rightly be called a copy. To assume, however, that a novice has taken the trouble to delve into the archives of the patent office and study the scattered theoretical elements of the Art and supply a new element to make a combination that is needed to produce a practical key-driven calculator, is not a probable assumption. But allowing such assumption were possible, it is evident that from anything that the Art disclosed prior to 1887 it was not possible to solve the concrete production of a key-driven calculator.

A conception which led to the final solution

In 1884, a young machinist, while running a planer, conceived an idea from watching its ratchet feed motion, which was indirectly responsible for the final solution of the multiple-order key-driven calculating machine. The motion, which was like that to be found on all planing machines, could be adjusted to ratchet one, two, three, four or more teeth for a fine or coarse feed.

While there is nothing in such a motion that would in any way solve the problem of the modern calculator, it was enough to excite the ambitions of the man who did finally solve it. It is stated that the young man, after months of thought, made a wooden model, which he finished early in 1885. This model is extant, and is illustrated on the [opposite page].

The inventor was Dorr E. Felt, who is well known in the calculating machine Art as the manufacturer of the “Comptometer,” and in public life as a keen student of economic and scientific subjects. The wooden model, as will be noted, was crude, but it held the nucleus of the machine to come.

“Macaroni Box” Model

Dorr E. Felt

Mr. Felt has given some interesting facts regarding his experience in making the wooden model.

Evolution of an invention

He says: “Watching the planer-feed set me to scheming on ideas for a machine to simplify the hard grind of the bookkeeper in his day’s calculation of accounts.

“I realized that for a machine to hold any value to an accountant, it must have greater capacity than the average expert accountant. Now I knew that many accountants could mentally add four columns of figures at a time, so I decided that I must beat that in designing my machine. Therefore, I worked on the principle of duplicate denominational orders that could be stretched to any capacity within reason. The plan I finally settled on is displayed in what is generally known as the “Macaroni Box” model. This crude model was made under rather adverse circumstances.

“The construction of such a complicated machine from metal, as I had schemed up, was not within my reach from a monetary standpoint, so I decided to put my ideas into wood.

Trials of an inventor

“It was near Thanksgiving Day of 1884, and I decided to use the holiday in the construction of the wooden model. I went to the grocer’s and selected a box which seemed to me to be about the right size for the casing. It was a macaroni box, so I have always called it the macaroni box model. For keys I procured some meat skewers from the butcher around the corner and some staples from a hardware store for the key guides and an assortment of elastic bands to be used for springs. When Thanksgiving day came I got up early and went to work with a few tools, principally a jack knife.

“I soon discovered that there were some parts which would require better tools than I had at hand for the purpose, and when night came I found that the model I had expected to construct in a day was a long way from being complete or in working order. I finally had some of the parts made out of metal, and finished the model soon after New Year’s day, 1885.”

The first “Comptometer”

By further experimenting the scheme of the wooden model was improved upon, and Felt produced, in the fall of 1886, a finished practical machine made of metal. This machine is illustrated on the [opposite page].

The Felt Calculating Machine

Referring to the [illustration of Felt’s first metal machine], it will be noted that the machine has been partly dismantled. The model was robbed of some of its parts to be used as samples for the manufacture of a lot of machines that were made later. In view of the fact that this machine is the first operative multiple-order key-driven calculating machine made, it seems a shame that it had to be so dismantled; but the remaining orders are operative and serve well to demonstrate the claims held for it.

Felt patent 371,496

The mechanism of the machine is illustrated in the reproduction of the [drawings of Felt’s patent, 371,496], on page 58. The specification of this patent shows that it was applied for in March, 1887, and issued October 11, 1887.

From the outward appearance of the machine it has the same general scheme of formation as is disclosed in the wooden model.

The First “Comptometer”

From Drawings of Felt Patent No. 371,496

Description of Felt calculator

The constructional scheme of the mechanism consists of a series of numeral wheels, marked A in the [patent drawings]. Each wheel is provided with a ratchet wheel, and co-acting with the ratchet is a pawl mounted on a disc E², carried by the pinion E¹, which is rotatably mounted on the same axis as the numeral wheel. The arrangement of these parts is such that a rotating motion given any of the pinions E¹, in a clockwise direction, [as shown in the drawings], would give a like action to their respective numeral wheels; but any motion of the pinions in an anti-clockwise direction would have no effect on the numeral wheels, owing to back-stop pawls K, and stop-pins T, provided to allow movement of the numeral wheels in but one direction.

Co-acting with each pinion E¹, is shown a long lever D, pivoted at the rear of the machine and provided with a segmental gear rack which meshes with the teeth of the pinion E¹. This lever comes under what is now generally termed a segment lever.

Each lever is provided with a spring S, which normally holds the front or rack end upward in the position shown in [Fig. 1], and has co-acting with it a series of nine depressable keys which protrude through the casing and contact with the upper edge of the lever.

The arrangement of the keys with their segment levers provides that the depression of any key will depress the segment lever of that order, which in turn will rotate the pinion E¹ and its numeral wheel.

While this arrangement is such that each key of a series gives a different degree of leverage action to the segment lever, and in turn a degree of rotation to the numeral wheel of the same order in accordance with the numerical value of the key depressed, it may be conceived that the momentum set up by the quick stroke of a key would set the numeral wheel spinning perhaps two or three revolutions, or at any rate way beyond the point it should stop at to register correctly.

To preserve correct actuation of the mechanism and overcome its momentum, Felt provided a detent toothed lever for each numeral wheel, which will be found marked J¹ in the [drawings]. To this lever he linked another lever G, which extended below the keys, and arranged the length of the key-stems so that when each key had revolved the numeral wheel the proper distance, the key will have engaged the lever G, and through the link connection will have caused the detent tooth of the lever J¹ to engage one of the pins T, of the numeral wheel, thus bringing the numeral wheel and the whole train of mechanism to a dead stop.

This combination was timed so that the (1) key would add one, the (2) key would add two, etc., up to nine for the (9) key. Thus the prime actuation of each wheel was made safe and positive.

Recapitulation of Art prior to Felt calculator

Before explaining the means by which the carry of the tens was effected in the Felt machine without interfering with multiple-order prime actuation, it will perhaps help the reader to recapitulate on what the Art already offered.

Going back to the Art, prior to Felt’s invention, there are a few facts worth reconsidering that point to the broadly new contributions presented in the Felt invention, and combining these facts with a little theory may perhaps give a clearer understanding of what was put into practice.

In most lines of mechanical engineering in the past, the term “theory ” connected with mechanical construction was a bugaboo. But the solution of the modern calculating machine was wholly dependent upon it.

Let us summarize on the Art, prior to Felt’s invention. A calculating machine that would calculate, if we eliminate the key-driven feature, was old. The key-driven feature applied to adding mechanism was old as adapted to a single-order machine with a capacity for adding only a single column of digits.

Why Hill failed to produce an operative machine

Hill attempted to make a multiple order key-driven machine, but failed because he did not theorize on the necessities involved in the physical laws of mechanics.

Hill saw only the columnar arrangement of the ordinal division of the keyboard, and his thought did not pass beyond such relation of the keys for conveyance. There is no desire to belittle this feature, but it did not solve the problem that was set forth in the specification and claims of his patent; neither did it solve it for anyone else who wished to undertake the making of such a machine.

Idiosyncrasies of force and motion increased by use of keys

The introduction of keys as a driving feature in the calculating machine Art demanded design and construction suitable to control the new idiosyncrasies of force and motion injected into the Art by their use, of which the elements of inertia and momentum were the most troublesome.

Light construction a feature

Hill, in the design and construction of his machine, ignored these two elementary features of mechanics and paid the penalty by defeat. The tremendous speed transmitted to the parts of a key-driven machine, which has already been illustrated, required that lightness in construction which is absolutely necessary to reduce inertia to a minimum, should be observed. The Hill machine design is absolutely lacking in such thought. The diameter of the numeral wheel and its heavy construction alone show this. Lightness of construction also enters into the control of momentum when the mechanism must suddenly be brought to a dead stop in its lightning-speed action. A heavily-constructed numeral wheel like that shown in the Hill patent would be as hard to check as it would to start, even if Hill had provided means for checking it.

Strength of design and construction, without the usual increase in weight to attain such end, but above all, the absolute control of momentum, were features that had to be worked out.

Robjohn partly recognized these features, but he limited the application of such reasoning to the prime actuation of a single order, and made nothing operable in a multiple key-driven machine.

Spalding and Bouchet recognized that the application of control was necessary for both prime actuation and carrying, but, like Robjohn, they devised nothing that would operate with a series of keys beyond a single order.

Operative features necessary

An operative principle for control under prime actuation was perhaps present in some of the single-order key-driven machines, but whatever existed was applied to machines with keys arranged in the bank form of construction, and, to be used with the keys in columnar formation, required at least a new constructive type of invention. But none of the means of control for carrying, prior to Felt’s invention, held any feature that would solve the problem in a multiple-order machine.

Classification of the features contained in the early Art of key-driven machines

While all the machines referred to have not been illustrated and described here, fair samples of the type that have any pertinence to the Art have been discussed, and those not illustrated would add nothing more than has been shown. A classification of the inventions referred to may be made as follows:

Parmelee and Stetner had no carrying mechanism; Hill, Robjohn, Borland and Hoffman, Swem, Lindholm and Smith had no control for the carry. Carroll, Bouchet and Spalding show a control for the carrying action, which in itself would defeat the use of a higher wheel for prime actuation, and which obviously would also defeat its use in a multiple-order key-driven machine.

One of the principal reasons why theory was necessary to solve the problem of the key-driven calculator existed in the impossibility of seeing what took place in the action of the mechanism under the lightning speed which it receives in operation. Almost any old device could be made to operate if moved slow enough to see and study its action; but the same mechanism that would operate under slow action would not operate correctly under the lightning-speed action they could receive from key depression. Only theoretical reasoning could be used to analyze the cause when key-driven mechanism failed to operate correctly.

Carrying mechanism of Felt’s calculator

Referring again to the [drawings of the Felt patent], which illustrate the first embodiment of a multiple-order key-driven calculating machine, we find, what Felt calls in the claims and specifications, a carrying mechanism for a multiple-order key-driven calculating machine. This mechanism was, as set forth in the specification, a mechanism for transferring the tens, which have been accumulated by one order, to a higher order, by adding one to the wheel of higher order for each accumulation of ten by the lower order wheel. This, in the Felt machine, as in most machines, was effected by the rotation of a numbered drum, called the numeral wheel, marked with the nine digits and cipher.

Transfer devices

The term “transfer device” for such mechanism was in common use, and as a term it fits certain parts of all classes of devices used for that purpose, whether for a crank-driven, key-driven, or any other type of multiple-order or single-order machine. But in the Felt invention we find it was not the simple device generally used for transferring the tens. It was, in fact, a combination of devices co-acting with each other which, in the specification of the patent, was termed the carrying mechanism.

Carrying mechanism versus mere transfer devices

Now, carrying mechanism may in a sense be termed a transfer device, as one of its functions is that of transferring power to carry the tens, but a mere transfer device may not be truthfully termed a carrying mechanism for a multiple-order key-driven machine unless it performs the functions that go to make up a correct carrying of the tens in that class of machine, and which we find laid down under the head of carrying mechanism in the Felt patents, where we find the first operative carrying mechanism ever invented for a multiple-order key-driven machine.

The functions demanded of such a piece of mechanism are as follows: First, the storing of power to perform the carry; second, the unlocking of the numeral wheel to be carried; third, the delivery of the power stored to perform such carry; fourth, the stopping and locking of the carried wheel when it has been moved to register such carry; and fifth, clearing the carrying-lock during prime actuation. A seemingly simple operation, but let those who have tried to construct such mechanism judge; they at least have some idea of it and they will no doubt bow their heads in acknowledgment of the difficulties involved in this accomplishment.

Mechanism for carrying the tens in single digit adders was one thing, and such as was used could well be called a transfer device; but mechanism for carrying the tens in a real key-driven calculating machine was another thing, and a feature not solved until Felt solved it, and justly called such combination of devices a “carrying mechanism.”

Details of Felt carrying mechanism

In the Felt machine, the carrying mechanism consisted of a lever and ratchet pawl action, constructed of the parts M, m², operated by a spring m, the pawl acting upon the numeral wheel pins T, to ratchet the wheel forward under the spring power. The power in the spring was developed from the rotation of the lower wheel, which through the means of an envolute cam[2] attached to left side of each wheel, operated the carrying lever in the opposite direction to that in which it was operated by the spring. As the carrying lever passed the highest point of the cam spiral and dropped off, the stored power in the spring retracted the lever M, and the pawl m², acting on the higher order wheel pins T, and moved it one-tenth of a revolution.

This part of the mechanism was in principle an old and commonly-used device for a one-step ratchet motion used in the carry of the tens. It served as a means of storing and transferring power from the lower wheel to actuate the higher wheel in a carrying operation, but a wholly unqualified action without control.

In the Felt machine a spring-actuated lever N, mounted on the same axis with the carrying lever, and provided with a detent stop-hook at its upper end, served to engage the numeral wheel at the end of its carried action, and normally hold it locked.

An arm or pin P, fixed in and extending from the left side of the carrying lever and through a hole in the detent lever, acted to withdraw the detent lever from its locking engagement with the numeral wheel as the carrying lever reached the extreme point of retraction; thus the wheel to be carried was unlocked.

Pivoted to the side of the detent lever is a catch O. This catch or latch is so arranged as to hook on to a cross-rod q, especially constructed to co-act with the catch and hold the detent lever against immediate relocking of the numeral wheel as the carrying lever and pawl act in a carrying motion. The latch has a tail or arm p, which co-acts with the pin P on the carrying lever in such a way as to release the latch as the carrying lever finishes its carrying function.

Thus the detent lever N is again free to engage one of the control or stop-pins T to stop and lock the carried numeral wheel when the carrying lever and pawl, through the action of the spring stored in the carrying, has moved the wheel the proper distance.

Bill for First Manufacturing Tools of the “Comptometer”

A lot of functions to take place in ¹/₁₆₅ of a second, but it worked. The timing of the stop and locking detents, of course, was one of the finest features.

Early Comptometer

The normal engagement of the carrying detent, it may be understood, would prevent the movement of the wheel by key action or prime actuation, but the patent shows how Felt overcame this.

The carrying stop and locking detent lever N is provided with a cam-arm or pin N, which was arranged to co-act with the cam disc E ([see Fig. 1]), fast to the prime actuating pinion E. The cam surface was short and performed its function during a short lost motion arranged to take place before the ratchet pawl would pick up and move the numeral wheel under key actuation.

The camming action was outward and away from the center, and thus released the carrying stop from its locking position with the numeral wheel, and continued rotation of the pinion and cam disc would hold the lock out of action until the parts had returned to normal.

With the return action of the keys, segment lever, pinion and cam disc, through the action of a spring attached to the segment lever, the carrying stop detent will again engage and lock the numeral wheel.

Manufacture of the Felt calculator

Felt really started to manufacture his calculating machine in the fall of 1886, after perfecting his invention. Having only a very limited amount of money with which to produce machines, young Felt, then but 24 years of age, was obliged to make the machines himself, but with the aid of some dies which he had made for some of the principal parts ([see reproduction of bill] for dies on opposite page), he was able to produce eight finished machines before September, 1887. Two of these machines were immediately put into service, for the training of operators, as soon as they were finished.

Trade name of Felt calculator

Of the first trained operators to operate these machines, which were given the trademark name “Comptometer,” one was Geo. D. Mackay, and another was Geo. W. Martin. After three or four months’ practice Mr. Martin demonstrated one of these machines to such firms as Sprague, Warner & Co., Pitkin & Brooks, The Chicago Daily News, and the Chicago, Burlington & Quincy R. R. Co., and finally took employment with the Equitable Gas Light & Fuel Co. of Chicago ([see letter on opposite page]) as operator of the “Comptometer.” The Gas Co. has since been merged with several other companies into the Peoples Gas Light & Coke Co. of Chicago.

A very high testimonial of the qualities of the Felt invention was given by Mr. Martin in 1888, a year after he entered the employment of the Gas Co., and is [reproduced on page 72].

Another fine testimonial was given by Geo. A. Yulle, Secy. & Treas. of the Chicago Gas Light & Coke Co., in September, 1888 ([see page 74]). Mr. Mackay, the other operator, secured employment with Albert Dickinson & Co., Seed Merchants, as operator of the “Comptometer.” Mr. Mackay was interviewed a few months ago, and was at that time, after thirty years, still with the same firm, and a strong advocate of the “Comptometer.”

Letter from Geo. W. Martin